1. Field of the Invention
The invention relates to amorphous electrode active material which has superior charging and discharging characteristics, and a lithium secondary battery which uses that amorphous electrode active material.
2. Description of the Related Art
As personal computers, video cameras, mobile phones and other such devices become smaller, lithium secondary batteries have come to be widely used as power sources in the fields of communication and information-related devices due to their high energy density. Also, in the automotive field as well, there is a push for the rapid development of electric vehicles due to environmental and resources issues, and lithium secondary batteries are being considered for use as power sources to power these electric vehicles.
Currently amorphous electrode active material is known to be used as the electrode active material in lithium secondary batteries. For example, Japanese Patent Application Publication No. 2005-135866 (JP-A-2005-135866) describes electrode active material that is mainly an amorphous metal complex represented by the general expression M2-2xB2xO3. Also, Japanese Patent Application Publication No. 8-78002 (JP-A-8-78002) describes positive electrode active material that is made up of an oxide of a transition metal from the 7A family or an oxide of a transition metal from the 8A family or both, in which a portion of that transition metal oxide has an amorphous structure. Further, Japanese Patent Application Publication No. 10-74515 (JP-A-10-74515) describes positive electrode active material in which a transition metal from the 7A family or a transition metal from the 8A family or both is Me, and in which a portion or all that has a LiMeO2 structure is made up of an amorphous metal oxide.
Amorphous electrode active material is advantageous in that the composition can be set freely compared with crystalline electrode active material. Moreover, although amorphous electrode active material shows promise as a high capacity electrode active material, its actual capacity is currently still low so there is a demand for high capacity amorphous electrode active material. Incidentally, Japanese Patent Application Publication No. 10-134813 (JP-A-10-134813) and Japanese Patent Application Publication No. 9-22695 (JP-A-9-22695) both describe electrode active material and the like which, although not amorphous, does consist mainly of an iron complex FeBO3 or the like.